1. Field of the Invention
The present invention relates to an improved method for fabricating a vehicle wheel constructed as a one-piece part from sheet metal and to a one-piece metal vehicle wheel constructed by the improved method.
2. State of the Prior Art
Vehicle wheels to be mounted on a vehicle and for supporting a tire thereon are usually made of metal. The fabrication of such metal wheels typically involves multiple components and multiple shaping and connecting operations. For example, a typical process presently employed to manufacture a metal wheel involves at least the following steps: Rolling an elongated rectangular piece of metal to form a rim; welding the ends of the rolled rectangular piece of metal to form a continuous cylindrical rim; cleaning the welded area; sizing the substantially cylindrical rim to its finished dimensions; separately fabricating an inside hub member and connecting, as by welding, the inside hub member to the interior of the rim.
A vehicle wheel fabricated from a single piece of metal requires less material to construct and is substantially simpler to fabricate as there are fewer parts to construct and there are no connecting steps involved, thus resulting in cost savings. In addition, one-piece construction eliminates stress concentrations, which can be associated with connections between non-integral components.
Vehicle wheels fabricated from a single piece of metal are known in the art. For example, U.S. Pat. No. 2,075,294 discloses a method of forming both the hub and rim of a vehicle wheel from a single forged or cast metal blank. The process involves a number of successive steps, such as forging, rolling, and forming steps, for producing a one-piece vehicle wheel.
U.S. Pat. No. 3,129,496 also discloses a manufacturing method for producing a wheel, including the rim and the hub portion thereof, from a single cylindrical blank. The cylindrical blank is constructed from an elongated rectangular piece which is rolled into a substantially cylindrical form, and the ends thereof are then welded together. The cylindrical blank is then formed into a wheel by a series of sequential steps, which include a roll extrusion step and a series of horizontal and vertical linear stroke die forming steps. Because this process involves at least one welding operation, however, the full advantages of a true one-piece construction are not realized.
Finally, British Patent 406,186 discloses a metal wheel formed from a single piece of sheet metal by a series of linear stamping operations, and Japanese Patent Application No. 60-13327 discloses a metal wheel formed from a single piece of sheet metal by a series of stamping and rolling operations.
While methods for fabricating one-piece metal vehicle wheels are known, there nevertheless remains the constant need and challenge to improve the strength, reliability, and cost effectiveness of a one-piece metal vehicle wheel while at the same time reducing the weight thereof and simplifying the fabrication thereof.